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Synopsis As the world becomes warmer and precipitation patterns less predictable, organisms will experience greater heat and water stress. It is crucial to understand the factors that predict variation in thermal and hydric physiology among species. This study focuses on investigating the relationships between thermal and hydric diversity and their environmental predictors in a clade of Hispaniolan anole lizards, which are part of a broader Caribbean adaptive radiation. This clade, the “cybotoid” anoles, occupies a wide range of thermal habitats (from sea level to several kilometers above it) and hydric habitats (such as xeric scrub, broadleaf forest, and pine forest), setting up the possibility for ecophysiological specialization among species. Among the thermal traits, only cold tolerance is correlated with environmental temperature, and none of our climate variables are correlated with hydric physiology. Nevertheless, we found a negative relationship between heat tolerance (critical thermal maximum) and evaporative water loss at higher temperatures, such that more heat-tolerant lizards are also more desiccation-tolerant at higher temperatures. This finding hints at shared thermal and hydric specialization at higher temperatures, underscoring the importance of considering the interactive effects of temperature and water balance in ecophysiological studies. While ecophysiological differentiation is a core feature of the anole adaptive radiation, our results suggest that close relatives in this lineage do not diverge in hydric physiology and only diverge partially in thermal physiology.
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Phylogenetic analysis of adaptation in comparative physiology and biomechanics: overview and a case study of thermal physiology in treefrogs
ABSTRACT Comparative phylogenetic studies of adaptation are uncommon in biomechanics and physiology. Such studies require data collection from many species, a challenge when this is experimentally intensive. Moreover, researchers struggle to employ the most biologically appropriate phylogenetic tools for identifying adaptive evolution. Here, we detail an established but greatly underutilized phylogenetic comparative framework – the Ornstein–Uhlenbeck process – that explicitly models long-term adaptation. We discuss challenges in implementing and interpreting the model, and we outline potential solutions. We demonstrate use of the model through studying the evolution of thermal physiology in treefrogs. Frogs of the family Hylidae have twice colonized the temperate zone from the tropics, and such colonization likely involved a fundamental change in physiology due to colder and more seasonal temperatures. However, which traits changed to allow colonization is unclear. We measured cold tolerance and characterized thermal performance curves in jumping for 12 species of treefrogs distributed from the Neotropics to temperate North America. We then conducted phylogenetic comparative analyses to examine how tolerances and performance curves evolved and to test whether that evolution was adaptive. We found that tolerance to low temperatures increased with the transition to the temperate zone. In contrast, jumping well at colder temperatures was unrelated to biogeography and thus did not adapt during dispersal. Overall, our study shows how comparative phylogenetic methods can be leveraged in biomechanics and physiology to test the evolutionary drivers of variation among species.
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- PAR ID:
- 10321069
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- Volume:
- 225
- Issue:
- Suppl_1
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1242/jeb.243292
